The invention concerns a connection end block to supply a sputter cathode with a coolant and electrical voltage.
In ordinary sputtering devices for high vacuum coating by cathode sputtering, plate-like targets are generally mounted on a magnetron and the material of the target then atomized by ion bombardment. Because of the rigid arrangement of the target and magnetron relative to each other, recesses or pits are formed with time in the target material at the sites at which the target material is preferentially atomized because of the magnetic lines of force. The yield of target material is relatively low on this account, since the target must be replaced prematurely.
To avoid this effect different solutions for sputtering devices have been proposed for use during coating of substrates by cathode sputtering. A rotatable sputter cathode is known from U.S. Pat. No. 4,356,073, which includes an elongated cylindrical tubular element, in addition to other components, which is provided with a layer of the desired coating material. A rotatable sputter cathode is also known from U.S. Pat. No. 4,443,318, which includes an elongated cylindrical tubular element, means to rotate the tubular element and a target device with coating material, which are releasably mounted on the tubular element.
In the mentioned solutions a situation can be achieved by rotating the tubular element in which material ablation occurs over the entire extent of the tube-target uniformly and in this way formation of recesses or pits of the target material is prevented.
The term sputtering device is to be understood to mean in this application an arrangement that includes at least one magnetron and sputter cathode with one or more targets.
To supply the sputtering device with coolant and electrical voltage so called connection end blocks are mounted within the vacuum chamber of the coating device, which have separate connections for a coolant and electrical power supply of the sputtering device arranged in the vacuum chamber. Both media are therefore fed separately to the connection end block and brought to the same electric potential in assemblies mounted in front. Current feed then generally occurs via sliding contacts. Transfer of the rotational movement to the target tube generally occurs by means of a second drive end block. A problem in these solutions is that the pressure behavior of the sliding contacts relative to the abrasion pattern is not optimal. Because of this the current feed is non-uniform. The relatively long conductors of the sliding contacts (also referred to as carbon brushes) cannot be directly cooled for contacts, so that especially during medium frequency operations, the current is limited by heating of the wires and therefore the admissible maximum temperature of the insulation. Potential adjustment of the cooling water must be carried out in an additional assembly. The conductors on the sliding contacts can exert a tensile load on the sliding contacts so that after assembly it is not ensured that the sliding contacts are pressed at the prescribed position with the prescribed force onto the shaft. The previous solution with tubes and wires on the supply end box leads to a high assembly expense and error possibilities during assembly.
Such connection end blocks are known, for example, from WO 2006/042808 A1, US 2004/0149576 A1 and WO 02/38826 A1.
In the solution according to WO 2006/042808 A1 a base with a contact ring and a spindle mounted to rotate coaxially in the base with a number of electrically conducting sliding contacts forced upward by elastic elements that produce electrical contact with the contact ring of the base [are used] for voltage supply. This solution has the main drawback that the propagation determined by the skin and proximity effect cannot be allowed for so that a restriction occurs in current carrying capacity. Another significant drawback is the limited decoupling of the sliding pair from the component tolerances. This solution requires reliable alignment of the participating partners in the sliding contact.
In the solution according to US 2004/0149576 A1 the sliding contact lies in cooling water. This solution is successful for DC operation. During medium frequency operation the current must flow over all bearings so that special precautions must be taken so that the bearings withstand the medium frequency current.
With the solution according to WO 02/38826 A1 a sliding contact lies in the vacuum. Very high friction coefficients occur in vacuum so that the sliding contacts wear inadmissibly rapidly and also release the abraded carbon into the vacuum chamber.
The task of the invention therefore consists of providing a connection end block to supply a sputtering device with a coolant and electrical power, which permits uniform current feed and potential equalization for the coolant without using additional assemblies.
These tasks are solved according to the invention by the connection end block described below.